The present invention relates to a low-noise block converter for use in a receiver for a satellite broadcasting system, and more particularly, to the low-noise block converter being capable of receiving two-band satellite broadcasting signals, especially for use in Europe.
Conventionally, a known satellite broadcasting system in Europe is constituted as shown in FIG. 1, in which it can be seen to be divided into FSS (Fixed Satellite Service; 10.95-11.7 GHz) and BSS (Broadcasting Satellite Service; 11.7-12.5 GHz). Accordingly, in order to receive a broadcasting signal from the satellite, BSS/FSS LNBs (low-noise block converter) 10,20 have been required to convert the super high frequency signal into IF signal, wherein, in order to select the signal of the corresponding band, a voltage of logic low/high (i.e., zero/12 Volts) has been applied at a FSS/BSS selection terminal SW1 of a satellite broadcasting receiver 30, so that either one of the BSS low-noise block converter 10 or the FSS low-noise block converter 20 is thereby selected to receive the signal.
FIGS. 2(A) and 2(B) each show in more detail the FSS low-noise block converter 20 and the BDD low-noise block converter 10. In the FSS low-noise block converter shown in FIG. 2(A), a low noise amplifier 21 amplifies a super high frequency signal of 10.95-11.7 GHz band inputted at a radio-frequency (RF) signal input terminal RFI1. The amplified signal is passed through a predetermined band of a band pass filter 22 so that in a mixer 23 it is mixed with an oscillating signal of 10 GHz from a local oscillator 24 and thereafter the mixed signal is amplified by an intermediate (IF) amplifier 25 to obtain at an IF output terminal IFO1 a signal of 0.95-1.7 GHz, which is used for the purpose of transmitting the picture image to a cable TV broadcasting station or the like. In the BSS low-noise block converter shown in FIG. 2(B), a super high frequency amplifier 31 amplifies a super high frequency signal of 11.7-12.5 GHz band inputted at a RF signal input terminal RFI2. The amplified signal is passed through the corresponding band of a band pass filter 32 and thereafter, in a mixer 33, is mixed with an oscillating signal of 10.75 GHz from a local oscillator 34 so that a signal of 0.95-1.75 GHz is outputted through a IF amplifier 35 to a IF output terminal IFO2, which is used for the purpose of transmitting the direct satellite broadcasting service to each home.
Accordingly, in order to receive the satellite broadcasting signals of two bands in the known system, each FSS and BSS low-noise block converters should be constituted separately, and in the satellite broadcasting receiver 30 the low/high voltages should be applied to a selection terminal SW1 for selecting one of the FSS and BSS low-noise block converters 10 and 20 so that the satellite broadcasting received signal of the corresponding band is selected. Therefore, the conventional system has a problem that its system construction such as the cable connection is complicated due to the use of a plurality of low-noise block converters.